Chris Pincher (wearing jacket) campaigns with the then Tory party leader, David Cameron, in 2010.
Photograph: Adrian Dennis/AFP/Getty Images

Conservative MP Chris Pincher has “voluntarily stood down” from the whips’ office and referred himself to the party’s complaints procedure and the police following an allegation about his behaviour, a Downing Street spokesman said.

The move came after two other Conservative MPs, Dan Poulter and Daniel Kawczynski, were referred to the party’s new internal party disciplinary system, it was announced on Sunday.

It means that four MPs will now be investigated under the process, announced by Theresa May last week. Stephen Crabb, the former pensions secretary, was referred on Saturday after admitting he sent suggestive text messages to a teenager.

Pincher, the MP for Tamworth was reported by the Mail on Sunday as making an unwanted pass at the former Olympic rower and Conservative activist Alex Story. The alleged incident reportedly took place with Pincher dressed in a bathrobe at his London home.

Pincher was appointed as a government whip in June, after serving as an assistant whip since July 2016.

Pincher reportedly said on Saturday evening: “I do not recognise either the events or the interpretation placed on them by the Mail on Sunday.

“Whatever may or may not have happened or been said was obviously many years before I became an MP. If Mr Story has ever felt offended by anything I said, then I can only apologise to him.”

A No 10 spokesman said: “Following a conversation with him, the chief whip has referred Daniel Poulter to the party’s new disciplinary committee for further investigation.”

Separately, a Conservative party spokesman said: “The chief whip has referred Daniel Kawczynski to the party’s new disciplinary committee for further investigation.”

Another Tory MP, Charlie Elphicke, has been suspended by the party following serious allegations that according to chief whip, Julian Smith, have been passed to the police.

Two ministers, Damian Green and Mark Garnier, face inquiries by the Cabinet Office under yet another system. Allegations of inappropriate behaviour against them are being looked into on the basis of whether they breached the ministerial code.

Downing Street did not say of what Poulter, the MP for Central Suffolk and North Ipswich since 2010, was accused. He reportedly denies any wrongdoing.

However, another Tory MP, Andrew Bridgen, wrote in the Sunday Times that he had chosen to “call out the alleged inappropriate behaviour” of Poulter. Bridgen said he had complained to Conservative whips in 2010.

Bridgen, the MP for North West Leicestershire, said his complaint was “met with no interest” from the whips and two years later Poulter was promoted to the post of junior health minister. Bridgen wrote: “While I appreciate that speaking out about an MP in my own party will not make me particularly popular and could damage my own career prospects, I have chosen to do so in the hope that it will encourage others, especially those who have been victims of sexual harassment, to come forward.”

A spokesman for Poulter said he “denies all allegations of misconduct or inappropriate behaviour and will vigorously defend himself against any such claims”.

The investigation to Kawczynski follows claims by Channel 4 News that the MP for Shrewsbury and Atcham sought to pressure a female researcher of another Tory MP to go on a date with a wealthy friend, who had seen her in parliament.

Eleanor Laing, the MP for whom the woman worked, has released a statement saying she was “very angry at this inappropriate behaviour and I strongly reprimanded my colleague in front of several witnesses”.

It is reported that Kawczynski does not deny he approached the woman but says he did nothing inappropriate.

May announced the new Conservative code of conduct in a letter to the Speaker of the Commons, John Bercow, about her party’s plans to tackle the issue.

The code states that inquiries should be conducted by a panel of three or more people, at least one of whom should be independent of the Conservatives.

The new code applies to MPs, peers, MEPs, members of the Scottish, Welsh and London assemblies, police and crime commissioners, elected mayors, councillors and party officials.

It compels them to “take reasonable steps” to ensure those who want to complain about harassment, bullying or discrimination are able to do so. There is an email address and phone number to which complaints can be made.

Harassment is defined as “any unwanted physical, verbal or non-verbal conduct that has the purpose or effect of violating a person’s dignity or creating an intimidating, hostile, degrading, humiliating or offensive situation or environment for them”.